Project Abstract Identification of genetic and epigenetic changes associated with disease states can afford deep insight into the underlying molecular processes, but, particularly for diseases of the central nervous system (CNS), translating this information to new drug therapies remains a challenge. Here, we will exploit the chemistry of pharmacophores found in psychoactive drugs to study the impact of genetic variants and epigenetic modifications in addiction. Hydrazine- based drugs including monoamine oxidase inhibitors (MAOI) have a long history of success in treating CNS disorders. The hydrazine group covalently inactivates several classes of enzymes (e.g. oxidases, oxygenases, demethylases, hydroxylases) in the CNS that participate in transcriptional regulation and chromatin remodeling, thereby contributing to a broad range of biological functions and disease pathologies. I previously developed a novel chemical proteomics discovery platform (which I dubbed `RP-ABPP) by exploiting the unique reactivity (reverse polarity, RP) of this pharmacophore to create unbiased probes to target these enzyme classes by activity-based protein profiling (ABPP). Given the established ability of hydrazine drugs to reach the CNS and manipulate its biochemistry, this project will implement first-in- class, nucleophilic brain-penetrating probes using our RP-ABPP platform to discover hydrazine- sensitive enzymes disrupted in preclinical models of drug addiction. Specifically, these probes will evaluate changes to the brain during the development of dependence using electronic nicotine delivery systems (ENDS) with a newly established mouse model of inhalation exposure. The goals are to i) identify novel druggable enzyme targets that are dysregulated in nicotine dependence and ii) develop a suite of selective probes that can be used by neuroscientists as pharmacological tools to study drug abuse and other psychiatric disorders. This platform is expected to i) create new opportunities to map functional consequences of genetic mutations and epigenetic modifications in drug dependence, ii) discover new druggable enzyme activities that can be spatially mapped by imaging, and iii) ultimately create a unique opportunity for therapeutic development around a relatively underexplored chemical space.